Tuesday, April 17, 2012

Pollen-collecting by stingless bees on cacao flowers !

Pollen-collecting by stingless bees on cacao flowers

I came across this very interesting abstract from a study of cacao pollination by meliponine bee Liotrigona parvula Darchen in Africa,(which would be a stngless bee species at least related to those found in Central and South America!).I have been interested in just how many stingless bees might exist in the so called 'Old World' including Africa.I had already been aware that stingless bees exist in Australia and were a source of honey for the Aborigenes.Also someone from Japan had told me their were stingless bees in South East Asia,particularly Thailand.What is new and exciting to me and no doubt to most people interested in cacao is that stingless bees may contribute however sslightly or not,to cacao pollination in Africa and I have just come across a similar claim being made by an investigator in Central America that another stingless bee species has been shown to pollinate cacao in Costa Rica and is competitive in that task with its midge or fly competitors,at least in situations where cacao is growing in direct sunlight !

Excuse the exclamation marks but this stingless bee-cacao pollination is big news and,even for most cacao experts,new news.If true it would show that at least one stingless bee can do the pollination of cacao generally believed done only by tiny flies or midges ! While the African observers appear to be saying that the stingless bee Liotrigona parvula Darchenmay very well be contributing to cacao pollination in cacao plantations,the Costa Rica observers appear to be saying the stingless bee taking pollen in diect sunlight in competition with midges may not be pollinating at all.Still stingless bees do pollinate other trees and crops and are valuable to a diverse ecology including in cacao agro-ecosystems.

Research Paper Dynamics of cocoa pollination: tools and applications for surveying and monitoring cocoa pollinators
E.A. Frimponga1 c1, I. Gordona2, P.K. Kwaponga1 and B. Gemmill-Herrena3 a1 Department of Entomology and Wildlife, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana a2 icipe – African Insect Science for Food and Health, PO Box 30772-00100, Nairobi, Kenya a3 AGPS – FAO, Viale Terme di Caracalla, Rome, Italy
Abstract
Pollinators are important natural agents for fruit and seed formation in most tree crops and the use of appropriate sampling methods is fundamental in studying their population. A study to develop surveying and monitoring protocols for cocoa pollinators was undertaken in Ghana. Yellow, white and blue UV-bright painted pan traps (UVPPT), McPhail traps and motorized aspirators were used to sample pollinators of cocoa for 13 successive months, after 6 days assessment of the effectiveness of the traps and diurnal active period of the pollinators. The peak pollinating period of cocoa by ceratopogonid midges was between 07.00 and 12.00 h, as previously reported. All three methods were effective in sampling ceratopogonid midges with the UVPPT being the most efficient in terms of sampling effort. The number of ceratopogonid midges caught by the yellow-UVPPT was significantly higher than that by blue- and white-UVPPT. The diversity of midges caught could not be determined due to taxonomic difficulties, and thus all the three colours of UVPPT should be used until efficiency in terms of diversity is determined. It is reported here that the meliponine bee Liotrigona parvula Darchen visits cocoa flowers and thus their effectiveness in cocoa pollination should be investigated. ..................................................

Stingless bees (Trigona jaty) routinely visit the flowers ofTheobroma cacao (Sterculiaceae) in the Atlantic lowlands of Costa Rica. The bees collect pollen and behave as pollen thieves in flowers well exposed to direct sunlight in cacao plantations, and avoid flowers in heavy shade. Pollination rates are maximized, however, in heavy shade due to the high abundance of the small-bodied pollinating midges (Ceratopogonidae and Cecidomyiidae) found in such places. Pollen-thieving by stingless bees, therefore, may only impact on fruit set in cacao trees in direct sunlight, with only minimal to no impact in areas of cacao where natural pollinator activity is high.

Key words Trigona jaty - pollination - cacao - sunlight - shade

This research was funded by grants from The American Cocoa Research Institute of the United States of America. I thank T. Noeske for statistical assistance.

Steam-distilled floral fragrance oils from nine distinctive cultivars ofTheobroma cacao L. (Sterculiaceae) in Costa Rica were examined with GC-MS to determine whether or not major differences existed among these cultivars for volatile constituents comprising 50% or more of the samples. The cultivars selected for floral oil analyses were chosen to represent diverse cultivars having supposedly different genetic backgrounds and histories of artificial selection for agronomic purposes. Cluster analysis revealed two major groupings of cultivars: those with higher molecular weight dominant compounds, and those having lower molecular weight compounds. Additionally, one cultivar, Rim-100, selected from criollo or ancestral-type cacao in Mexico and resembling criollo in the appearance of flowers and fruits, formed an extreme group having the highest molecular weight profile for major volatile compounds. Based upon these analyses, bioassays using McPhail traps were performed in an abandoned cacao plantation in northeastern Costa Rica during rainy and dry seasons to determine the relative attraction of these oils to flying insects. Bioassays revealed that the Rim-100 cultivar attracted by far the greatest numbers of cacao-associated midges (Diptera: Ceratopogonidae and Cecidomyiidae), as well as stingless bees (Hymenoptera: Apidae: Meliponinae), suggesting that a floral fragrance having high-molecular-weight volatiles is more potent as an attractant to flying insects than floral oils having lower-molecular-weight compounds. It is suggested that Rim-100 more closely resembles an ancestral or wild-type cacao than the other cultivars examined, and therefore it is more effective in attracting opportunistic dipteran floral visitors and pollinators than other cultivars in plantation settings. Several of the major volatile compounds found in the floral oils ofT. cacao and other species ofTheobroma occur in mandibular and other exocrine glands in various bees, including stingless bees and halictids, known visitors ofTheobroma flowers. These compounds are particularly present in noncultivated species ofTheobroma and have much more noticeable fragrances than the seemingly scentless flowers of cultivatedT. cacao selected for agriculture. It is hypothesized that the floral attraction system of ancestral or wild (noncultivated)T. cacao and other species ofTheobroma may have evolved to attract certain bees as their principal pollinators in natural habitats in the Neotropics, with a floral reward hypothesized as being sociochemicals needed by bees for mating, foraging, territorial defense, etc. Because of the many generations of extensive selection by cloning for desired cultivars,T. cacao might have lost much of its original floral attraction system for bees, instead being pollinated opportunistically by dipterans in plantation habitats. This may help to explain why natural pollination in cultivatedT. cacao is generally very poor relative to observed levels of fruit-set in wild or noncultivated species ofTheobroma.

Abstract: Aims (1) To determine whether deforestation has affected the incidence of species of Melipona in an area undergoing deforestation. (2) To highlight the potential use of GIS and remote-sensed environmental variables in studies of insects as bioindicators of landscape change. Location Central Rondonia, Brazil in the south-western Amazon Basin, an area under intense deforestation pressure for agriculture and cattle ranching since the 1970s. Methods Stingless bees of the genus Melipona were sampled outside of forest cover on iron-weed, Vernonia polynthes Less., at 69 locations along a deforestation gradient within a 3150-km2 study area. We related species richness and composition for each sample point to local and regional deforestation variables, including geographical position along the deforestation gradient, distance to the forest, and percentage of primary forest coverage within a 1 and 2 km radius of the sample points. Deforestation variables were generated using GIS and LANDSAT TM imagery of the study area. Redundancy analysis was used to illustrate the relationship between species incidence, the deforestation variables, and other possible confounding environmental variables. Results Seven species were found within the study area. Two species (M. seminigra abunensis Cockerell, 1912 and M. grandis Guérin, 1844) appear not to be affected by deforestation yet, occurring evenly across the deforestation gradient. Two other common species (M. melanoventer Schwarz, 1932 and M. rufiventris brachychaeta Moure, 1950), however, occurred mainly towards the end of the gradient where the forest was more intact, indicating relative susceptibility to deforestation. Melipona species richness, ranging from 1 to 5 species, was inversely related to distance to forest and directly related to percentage of forest cover. Main conclusions Adverse effects of deforestation on Melipona are detectable in the study area, despite the fact that significant areas of tropical forest cover remain. The species that are most affected may be considered indicators of landscape change, and efforts to protect these species could involve their use in beekeeping programmes designed to raise rural incomes and maintain regional biodiversity.